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I was talking to friend today about a rifle he's building. He said he was getting his barrel from Black Hole Weaponry which uses polygonal rifling in their barrels.
I've heard of polygonal rifling on a TV show but never bothered to look into it until today.

I am also considering building a new upper & was wondering if anyone would care to weigh in on it? It seems like a good idea as long as one uses jacketed bullets. It apparently lasts longer & reaches higher velocities than a standard cut barrel of the same caliber & length :ponder:
Anyone know differently?